GB2025785A

GB2025785A - Method and apparatus for regenerating an adsorbent

Info

Publication number: GB2025785A
Application number: GB7915786A
Authority: GB
Original assignee: Bowe Maschinenfabrik GmbH; Boewe Boehler and Weber KG
Current assignee: Bowe Maschinenfabrik GmbH; Boewe Boehler and Weber KG
Priority date: 1978-05-12
Filing date: 1979-05-08
Publication date: 1980-01-30
Also published as: IT1112803B; DE2820771B2; FR2425266A1; JPS6218208B2; IT7922369A0; US4282015A; DE2820771A1; GB2025785B; FR2425266B3; JPS54149378A; DE2820771C3

Description

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GB 2 025 785 A 1

SPECIFICATION

Method and Apparatus for Regenerating an Adsorbent

The present invention relates to a method and 5 apparatus for regenerating an adsorbent. The method and apparatus are particularly suitable for use in systems in which two containers filled with adsorbent are provided only one of which is utilised for adsorption at any one time, Thus, one 10 container contains still unsaturated adsorbent for the adsorption of gasesous substances or materials whilst the other container contains adsorbent saturated with such substances and materials, which adsorbent is to be regenerated whilst 15 adsorption is taking place in the other container.

It is known to regenerate adsorbent by passing steam therethrough and condensing the steam and any gaseous material entrained therewith. When utilising chemical cleaning , degreasing and 20 similar machines in which the air exhausted therefrom contains solvent gases, the air is usually returned to the machine in a closed circuit through an adsorption device so as to prevent air which still contains solvent gas residues from 25 escaping into the atmosphere.

In most known systems, the adsorption system comprises two containers containing an adsorbent, adsorption being alternated between the two containers such that solvent vapours 30 may be constantly adsorbed in one or other of the containers thereby permitting the adsorbent in the container not in use to be regenerated with steam.

In such known systems, the steam, after 35 passing through an adsorbent such as activated carbon, is passed into a condenser. The steam, together with any solvent vapours entrained therein is thus condensed. Any solvent gas-containing air present in the adsorption container 40 before the entry of the steam is exhausted into the atmosphere through the condenser and through a water separator connected thereto. Solvent gas therefore passes into the atmosphere which is ecologically undesirable. 45 The present invention therefore seeks to provide a method and apparatus which prevent gas-containing air present in one container from escaping into the atmosphere during the regeneration of the adsorbent and also prevent 50 solvent gas residues and undesired moisture from damaging other parts of the system.

According to the present invention, there is provided a method of regenerating adsorbent in a system comprising at least two containers each 55 filled with adsorbent, at least one container, at any moment in time, being capable of adsorbing gaseous material contained in an airstream, and the adsorbent in at least one of the containers requiring regeneration, wherein steam is 60 introduced into the container containing adsorbent requiring regeneration, the introduction of the steam causing the air containing gaseous material within the container to be displaced, passing the displaced air into the

65 inlet of the container capable of adsorbing gaseous material, providing a temperature or other sensor in the conduit connecting the two containers, actuation of said sensor causing the closing of a valve located in said connecting 70 conduit thereby causing said steam to be passed into a condenser.

This causes most of the air contained in the container containing adsorbent to be regenerated and to be forced, by the steam, into the other, still 75 active adsorption container. The air passes through the adsorbent material and any gaseous material or substances still contained therein are adsorbed. Accordingly, very little, if any, gas residues can escape. The air, after it has passed 80 through the adsorbent, may be conducted, in a closed circuit, from the adsorption container back from whence it was extracted by suction into the adsorption container. This may, for example, be a dry cleaning machine. Preferably, the air in the 85 other container, after passing through the adsorbent and when a preselected pressure is exceeded, is conducted into the ambient atmosphere.

Also according to the present invention, there 90 is provided an apparatus for regenerating an adsorbent comprising at least two containers each filled with an adsorbent, each container being provided with an inlet and outlet conduit for passing an airstream containing gaseous material 95 through the adsorbent, valve means being provided for alternately connecting one of the containers to the source of the airstream and for returning the airstream having had the gaseous material removed therefrom to the source, 100 wherein at least one of the containers, at any moment in time, being capable, of adsorbing the gaseous material and at least one of the other containers containing adsorbent requiring regeneration, each container having supply and 105 discharge conduits for steam utilised to regenerate the adsorbent, the supply and discharge conduits being to located that, in use, steam is passed through the containers in a direction opposite to the direction of flow of the 110 airstream, valve means for alternately supplying steam to the containers wherein the steam discharge conduits of the containers each lead to a condenser through discharge valve means, the conduits being interconnected through a conduit 115 containing a temperature sensor, the steam supply and discharge valves of each container are coupled with the steam discharge vaive in the steam discharge conduit of the other container such that opening one also opens the other, the 120 steam discharge valve in the steam discharge conduit of the other container being closed by a switching mechanism, which mechanism is actuated by the temperature sensor in the connecting conduit whereby the valve is closed 125 when a predetermined temperature is reached.

In such an apparatus the air displaced from the adsorption container in which regeneration is taking place, is passed through the other, still active adsorption container whilst the connecting

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conduit, as soon as the steam therein has penetrated to the temperature sensor, is shut down so that the residual steam enters the condenser where it is condensed together with 5 any gaseous material contained therein.

By so doing, no excess pressure occurs in the condenser. The only possible place at which an excess pressure can occur is at the outlet side of the other adsorption container through which the 10 displaced air has been passed. Since, on this side of the container, the air has already passed through the adsorbent and is free of solvent, it may be released harmlessly into the ambient atmosphere. Accordingly, an excess pressure 15 safety device permitting this to occur may be provided at the outlet of the container. A particularly simple embodiment of the invention provides for this excess pressure safety device to be in the form of a water seal or trap which is 20 connected to the air outlet of both containers.

After regeneration with the steam, the wet adsorbent may be dried, within the container by means of heated air or heated gas. With the first burst of air which is passed through the 25 adsorbent, very thick clouds of gas, the so-called vapours, are forced out of the adsorbent. In known installations these vapours are mostly conducted into a waste air flue. In a preferred embodiment of the invention, the drying occurs in 30 a closed circuit which leads from the adsorbent through a condenser, a fan and an air heater back to the adsorbent. No steam vapours can thus escape from the system into the ambient atmosphere. It is necessary, however, in such a 35 case to prevent dampness from entering the fan from the condenser which could cause damage thereto.

To protect the fan from dampness, and also from attack during the steam regeneration phase 40 from undesired steam residues, a desired aspect of the invention provides that, within the closed circuit, at the output of the condenser and upstream of the input of the fan, an air shut-off device, which may be a valve. This valve is 45 opened only periodically for drying the contents of the container. This prevents moisture from entering the fan both during the steam regeneration and during vapour drying. Since, at both these times, the air shut-off device is closed. 50 As soon as the last steam vapours in the condenser have been condensed, the air shut-off device can be re-opened.

Advantageously, therefore, the air cut-out device is formed as a water seal or trap which is 55 provided within a housing surrounding the condenser, the housing being connected, through a switchable valve to a water supply, the housing being connected to a water separator from the lowermost point of the housing through a second 60 switchable valve, and from a higher point in the housing, the housing being divided into two chambers by means of a wall extending downwardly to below the upper point leading to the water separator, the chambers being 65 separable by the water seal, whereby the inlet opening connecting the condenser to the adsorption container and the cooling means of the condenser are provided on one side of the wall, the outlet opening of the housing, which is connected to a fan, is provided on the other side of the wall, the first and second switchable valves, in use, never being both open or both closed. By so doing, the fan is also protected against moisture or dampness when it is located in a closed circuit. The provision of an air shut-off device at the condenser output is, as can be readily seen, independent of the number and type of adsorption containers being utilised.

Desirably, the wall is tubular and extends from the upper surface of the condenser housing into the lower region of the housing.

The invention will be further described, by way of example, with reference to the accompanying drawings in which:

Fig. 1 shows, schematically, an adsorption apparatus including two activated carbon containers and

Fig. 2 shows a condenser, and associated conduit means, forming part of the apparatus shown in Fig. 1.

The apparatus shown in Fig. 1 includes two containers 1, 2 filled with activated carbon, each container being connected through conduits 11 and 12 incorporating valves 3 and 4, or 5 and 6, to the outlet 8 and the inlet 9 of one or more chemical treatment devices 7. When the inlets and outlets 9 and 8 are open, a fan 10 located in the treatment device blows solvent-containing air in the direction of the arrow from the device into one of the adsorption containers 1 or 2 and, after passage through the carbon wherein the solvent is removed from the air, such air is induced, in a closed circuit, back into the treatment device.

In the example shown, it will be assumed that the adsorbent in the container 2 is saturated with solvent. It is therefore necessary to cause the solvent-containing air to pass through the container 1. The valves 3 and 4 are therefore opened and the valves 5 and 6 are closed. Control of the valves, and the connection and disconnection of the remaining components of the apparatus to be described hereinafter, is effected in a known manner by utilising a suitably programmed control mechanism 16'.

For regenerating the adsorbent in the container 2, valves 13,14 and 15 are opened, and steam is introduced into the container 2 from the conduit 17, the steam passing through a steam super heater 16 and an air heater 18. The heater 18 is not operated at this stage. Simultaneously with the opening of the valve 13, valve 19 is also temporarily opened. The simultaneity is effected by the control lines 21 and 22 which are linked to the valve 13 and are connected by a control mechanism 23. Valve 20, however, remains closed.

The gas in the container 2, that is to say, the solvent-containing air, is forced out by the steam and passes into the container 1 through a conduit 24 and the valve 19, wherein it passes through

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the activated carbon. If, in this manner, an excess pressure occurs on the secondary side, then air which has been substantially freed from solvent gas may escape into the atmosphere through a f 5 water trap or seal 26 and a ventilation conduit 27 connected thereto.

When the steam discharged from the container 2 arrives in the conduit 24, it passes a temperature sensor 25 provided therein, which 10 actuates the control mechanism 23 so as to close the valve 19. The steam then passes into a conduit 28 and thence into a condenser 29 where both the steam and the solvent gas contained therein are condensed.

15 If the contents of the container 1 are to be regenerated with steam and the container 2 is to be used for adsorption, a similar sequence is followed except that valves 5 and 6 are opened and valves 3 and 4 are closed. In such a case, 20 during regeneration, air is displaced from the container 1 into the container 2 and, after passage through the activated carbon, passes through the water trap 26 into conduit 27. The valve 13 is, in this case closed by the temperature 25 sensor 25 when the steam in the conduit 24 is at a temperature in excess of a predetermined temperature.

After such steam treatment, the wet adsorbent, e.g. that in container 2, is dried. This is 30 effected by opening valve 31 and closing valve 15 and passing air over the heater 18, through the container 2 and into the condenser 29 by means of a fan 30. At the beginning of the drying stage, a considerable amount of steam is driven off the 35 warm and damp adsorbent. A water seal or trap 31 is therefore provided in the condenser housing 29, which prevents the moisture passing into the fan 30. A non-return valve 32 is provided through which air may by induced by the fan 30 from the 40 ambient atmosphere.

An annular wall 34 is provided within the condenser housing 29. This wall extends from the upper end of the housing 29, surrounding an outlet opening 33 leading to the fan 30, into the 45 lower region of the housing, terminating below the level of the water. Externally of the wall 34, the cooling unit 35 of the condenser is located. This is supplied with cold water through conduit 36. The cooling water leaves the condenser 50 through conduit 37. The condenser has an inlet 42 through which the steam and air enters, which inlet is also located outside the wall 34. In the base of the condenser housing 29, a conduit 39 leading to a water separator 38 is provided, 55 though a valve 40. An overflow conduit 41 leads from the side wall of housing 29, at a level which is slightly above the lower end of wall 34, into the - conduit 39. The water outlet conduit 37 has a branch conduit 43 incorporating a valve 44 60 leading off therefrom, which conduit leads back into the interior of the housing. This permits the cooling water to be utilised for maintaining the water level inside the housing 29.

During the passage of steam through the 65 apparatus and at the beginning of the drying stage utilising heated air, the vapour emanating from the adsorbent is to be conducted into the condenser and condensed therein. Accordingly, the valve 44 is opened, and the valve 40 closed. 70 Accordingly, in the lower region of the housing 29, a water seal or trap 31 is formed, the level of which extends to the point of connection of the overflow conduit 41. Steam and moisture are thereby prevented from flowing into the conduit 75 45 leading to the fan 30.

As soon as the major portion of the vapour has been displaced from the adsorbent and the steam vapours have been condensed in the condenser, the valve 40 is opened and valve 44 is closed. The 80 water forming the seal or trap thereby flows out of the housing and air can flow through the condenser from the inlet opening 42 to the outlet opening 33 and thence to the fan 30. The valves 40 and 44, as previously mentioned, are 85 controlled by the programme control mechanism 16' in a known manner.

Claims

1. A method of regenerating adsorbent In a system comprising at least two containers each

90 filled with adsorbent, at least one container, at any moment in time, being capable of adsorbing gaseous material contained in an airstream, and the adsorbent in at least one of the other containers requiring regeneration, wherein steam 95 is introduced into the container containing adsorbent requiring regeneration, the introduction of the steam causing the air containing gaseous material within the container to be displaced, passing the displaced air into the inlet of the 100 container capable of adsorbing gaseous material, providing a temperature or other sensor in the conduit connecting the two containers, actuation of said sensor causing the closing of a valve located in said connecting conduit thereby 105 causing said steam to be passed into a condenser.

2. A method as claimed in claim 1, wherein the air in the other container, after passing through the adsorbent and when a preselected pressure is exceeded, is conducted into the ambient

110 atmosphere.

3. An apparatus for regenerating an adsorbent comprising at least two containers each filled with an adsorbent, each container being provided with an inlet and outlet conduit for passing an

115 airstream containing gaseous material through the adsorbent, valve means being provided for alternately connecting one of the containers to the source of the airstream and for returning the airstream having had the gaseous material 120 removed therefrom to the source, wherein at least one of the containers, at any moment in time, being capable of adsorbing the gaseous material and at least one of the other containers containing adsorbent requiring regeneration, each 125 container having supply and discharge conduits for steam utilised to regenerate the adsorbent, the supply and discharge conduits being so located that, in use, steam is passed through the containers in a direction opposite to the direction

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of flow of the airstream, valve means for alternately supplying steam to the containers wherein the steam discharge conduits of the containers each lead to a condenser through 5 discharge valve means, the conduits being interconnected through a conduit containing a temperature sensor, the steam supply and discharge valves of each container are coupled with the steam discharge valve in the steam 10 discharge conduit of the other container, such that opening one also opens the other, the steam discharge valve in the steam discharge conduit of the other container being closed by a switching mechanism, which mechanism is actuated by the 15 temperature sensor in the connecting conduit whereby the valve is closed when a predetermined temperature is reached.

4. An apparatus as claimed in claim 3, wherein the air outlets from the containers are connected

20 to an excess pressure safety device.

5. An apparatus as claimed in claim 4, wherein the excess pressure safety device is a water seal or trap.

6. An apparatus as claimed in any one of 25 claims 3 to 6 wherein the steam supply and discharge conduits of the containers are each adapted to be individually connected in series to a condenser, a fan and an air heater so as to form a closed circuit.

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7. An apparatus as claimed in claim 6, wherein a switchable air cut-out device is provided at the outlet of the condenser, the opening of which permits drying of the regenerated adsorbent in the container.

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8. An apparatus as claimed in claim 7, wherein the air cutout device is formed as a water seal or trap which is provided within a housing surrounding the condenser, the housing being connected, through a switchable valve to a water 40 supply, the housing being connected to a water separator from the lowermost point of the housing through a second switchable valve, and from a higher point in the housing, the housing being divided into two chambers by means of a 45 wall extending downwardly to below the upper point leading to the water separator, the chambers being separable by the water seal, whereby the inlet opening connecting the condenser to the adsorption container and the 50 cooling means of the condenser are provided on one side of the wall, the outlet opening of the housing, which is connected to a fan, is provided on the other side of the wall, the first and second switchable valves, in use, never being both open 55 or both closed.

9. An apparatus as claimed in claim 8, wherein the wall is tubular and extends from the upper surface of the condenser housing into the lower region of the housing.

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10. A method of regenerating adsorbent substantially as hereinbefore described.

11. An apparatus for regenerating adsorbent constructed and arranged to operate substantially as hereinbefore described with reference to and 65 as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1980. Published by the Patent Office. 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.